CAMBRIDGE, Mass., July 23 -- What began as a prominent African American professor's dispute with a white police sergeant grew more complex Thursday as the officer spoke publicly for the first time and a fuller portrait of his life emerged.

Sgt. James Crowley said Harvard scholar Henry Louis Gates Jr. was combative from the moment the officer arrived at his house last week to respond to a call about a possible burglary. As the confrontation escalated, Crowley said he warned Gates that he risked arrest.

"The second warning was with me holding a set of handcuffs in my hands -- something I really didn't want to do," Crowley said in a radio interview. "The professor at any time could have resolved the issue by quieting down and/or going back inside his house."

Crowley's account came on a day of dizzying debate over his actions, a furor that was touched off by President Obama's remarks at a news conference Wednesday night, when he linked Gates's arrest to the nation's long history of racial profiling and said the police had "acted stupidly."

The events drew Obama into the first racial controversy of his presidency. The personalized critique was rare for a president, and demonstrated the perspective Obama brings to the Oval Office.

"Three years ago, we would not have been having this conversation in this way," said Eddie S. Glaude, a professor of theology and African American studies at Princeton.

Obama stood by his criticism, telling ABC News's Terry Moran he was "surprised" his statement had sparked such controversy.

"I think it was a pretty straightforward commentary that you probably don't need to handcuff a guy, a middle-aged man who uses a cane, who's in his own home," Obama told Moran in an interview set to air Thursday evening on "Nightline," excerpts from which were made available online.

The president called Crowley an "outstanding police officer" but emphasized that "it doesn't make sense to arrest a guy in his own home if he's not causing a serious disturbance."

After reports of Gates's arrest surfaced in the media, the charge -- disorderly conduct -- was dropped. Gates said he believes he did nothing that would have justified Crowley's actions, and the officer's police report makes it clear he concluded before the arrest that Gates was in his own home.

On Thursday, the Cambridge police commissioner, Robert C. Haas, described the department as "deeply pained" by Obama's criticism and said Crowley had followed proper protocol in making the arrest.

"I do not believe his actions were in any way racially motivated," Haas said. "Sergeant Crowley is a stellar member of this department and I rely on his judgment every day. He was thrust into a crime in progress, and he tried to work his way through the situation."

Crowley grew up in a predominantly Irish Catholic neighborhood, where his family attended Mass regularly. The Boston Globe reported that in 1993, when he was working as an officer with the Brandeis University police force, he tried to resuscitate Boston Celtics star Reggie Lewis, who suffered a heart attack during a practice and died.

Crowley joined the Cambridge Police Department and was eventually tapped to teach a class on racial profiling at a police training academy.

Thomas Fleming, director of the police academy at the Lowell Police Department, which has a partnership with the Cambridge Police Department, said Crowley has taught the course for five years and has trained 300 recruits, none of whom have complained about him.

"He's a very professional police officer and he's a great instructor," Fleming said in a phone interview from his home.

Crowley arrested Gates last week after a neighbor called police to say someone appeared to be trying to break into a home. In fact, Gates was returning from an overseas trip and could not get his locked front door open.

When Crowley arrived and questioned whether Gates lived in the home, the 58-year-old academic became upset, eventually demanding the officer's name and badge number so he could file a complaint. Crowley said Gates referred to Crowley's mother as a way of showing his displeasure.

When the officer repeatedly asked Gates to speak with him outside, the professor responded, "Ya, I'll speak with your mama outside," Crowley wrote in a police report.

"I'm still just amazed that somebody of his level of intelligence could stoop to such a level, and berate me, accuse me of being a racist or racial profiling," Crowley said in a radio interview Thursday with WEEI-AM. "And then speaking about my mother, it's just -- it's beyond words."

Crowley, 42, said that, when he first saw Gates, in "my mind, I'm thinking, 'He does not look like someone who would break into the house.' " At the same time, however, "from the time that he opened the door, it seemed that he was very upset, very unhappy that I was there."

Of Obama, Crowley said in an interview with Boston's WBZ-AM: "I support the president of the United States 110 percent. I think he's way off base wading into a local issue without knowing all the facts as he himself stated before he made that comment."

What also became clear Thursday was that, because of Obama's comments, the issue was suddenly freighted with political significance.

In response to a question about the arrest asked Wednesday at the prime-time news conference, Obama said racism "still haunts us," even as his own election in November shows "the incredible progress that has been made."

"Now, I don't know, not having been there and not seeing all the facts, what role race played in that," the nation's first African American president said. "But I think it's fair to say, number one, any of us would be pretty angry; number two, that the Cambridge police acted stupidly in arresting somebody when there was already proof that they were in their own home."

On Thursday, commentators on the conservative National Review Web site called Obama's remarks "odd" and "shameful," while the Huffington Post's Norm Stamper posited that the president, though perhaps wrong to use the word "stupidly," may have struck an important blow for community-police relationships.

Michael Eric Dyson, a prominent black scholar and sociology professor at Georgetown University, said he was pleased that Obama, not known for publicly discussing race issues, weighed in on the matter of Gates's arrest.

"It's wonderful the president spoke up and used the bully pulpit to talk about an issue that all of us should be engaged in talking about," Dyson said. "The reason this thing has struck such a chord is because his story's not unique."

Gates is founding editor of The Root, an online magazine owned by the Washington Post Co.

Haas said he hoped the controversy might have ended when the criminal charge was dropped. But after a private meeting at police headquarters that lasted much of the day, he said Thursday that he had decided to create a panel of "independent, notable professionals" to study the entire record of Gates's arrest and issue a public report.

"Nobody is happy about this situation," Haas said. "This is not the kind of notoriety we want to come to this city. We have worked very hard for many years to improve our professional standing."

Research editor Alice Crites contributed to this report. Cheryl Thompson reported from Washington.